FIG. 1 shows a conventional reel drive mechanism, such as in a VCR, for providing a rotational drive for the supply and take-up reels of the cassette tape in which magnetic recording medium is accommodated. As shown in FIG. 1, the mechanism include a reel hub 14 for revolving with a reel of the cassette tape, a reel disc 16 having a tubular journal bearing portion which is assembled inside the reel hub 14, a torque transmitting plate 20 provided with the tubular journal bearing portion and tightly fitted inside the reel hub 16, a flat ring-type felt 18 placed between the reel drive gear 17 and the torque transmitting plate 20, helical springs 15 disposed to provide a frictional force so that gear 17 is urged against plate 20 through felt 12, and a mounting shaft 12 on which the above-mentioned elements are mounted so as to be rotational. With this conventional design configuration, if the reel drive gear 17 is engaged to, and rotatably driven by, a last-stage gear in a driver gear train, then the torque transmitting plate 20, in tight surface contact with the reel drive gear 17 by spring 15, begins to rotate about the mounting shaft 12, and therefore carries the twisting moment onto the reel hub 14 through the reel disc 16.
In this type of conventional drive mechanism design, the clutching force is generated between the reel drive gear 17 and the torque transmitting plate 20 by the spring force applied on the upper surface of the reel drive gear 17. This clutching force may be appropriately adjusted by proper selection of the spring constant so that a proper transmission of driving torque can be provided and, at the same time, the transmission of an overload twisting moment is prevented because of the slip on the upper surface of the flat ring-type felt 18.
Due to the fact that several elements must be employed in the conventional design in order to ensure the proper transmission of the driving torque (and to prevent an overload twisting moment), the cost of manufacture is high and the disassembly as well as the assembly of the mechanism is difficult. In addition to these problems, the bulky volume of the conventional reel drive mechanism has proven to be a significant hindrance to recorder/player design improvement, specifically, improved design to lower the weight and volume, especially the thickness, of the elements.